Seasonal Expression of Gonadotropin Genes in the Pituitary and Testes of Male Plateau Zokor (Eospalax baileyi)

Abstract

The gonadotropins, luteinizing hormone (LH) and follicle stimulating hormone (FSH), are glycoprotein hormones in the hypothalamic-pituitary-gonadal (HPG) axis and regulate mammalian reproduction. The expression of these genes in the plateau zokor (Eospalax baileyi) is poorly understood. We characterized the immunolocalization of the luteinizing hormone receptor (LHR) and follicle stimulating hormone receptor (FSHR) in the testes and evaluated the positive immunohistochemical results and the relative mRNA expression of gonadotropin genes. During the non-breeding season (September), the relative testes weight and the seminiferous tubule diameter were significantly reduced. All germ cell types were observed during the breeding season (May), whereas only spermatogonia were observed during the non-breeding season. LHR was present in the Leydig cells whereas FSHR was present in the Sertoli cells. The mean optical density was higher during the breeding season. The mRNA expression of LHβ and FSHβ was lower in the pituitary but LHR and FSHR genes expression were higher in the testes during the breeding season. These data elucidate the expression of gonadotropin genes in the HPG axis of the male plateau zokor and suggest that gonadotropins play a vital role in the regulation of seasonal breeding.

Keywords: LHR and FSHR; LHβ and FSHβ; RT-PCR; plateau zokor; seasonal reproduction.

Figure 1

The testicular morphology, weights, and histology of plateau zokor (Eospalax baileyi) during the transition from the breeding to the non-breeding season. (A): the plateau zokor, (B): the testes after fixation, (C): the relative testes weight of plateau zokor during the breeding and the non-breeding seasons, (D): the seminiferous tubule diameter of plateau zokor during the breeding and the non-breeding seasons, and (E,F): the histological change of the testes from the breeding season (E) to the non-breeding season (F). Scale bars, 100 µm. SC, Sertoli cell; LC, Leydig cell; Spg, spermatogonia; pSpc, primary spermatocyte; sSpc, secondary spermatocyte; eSpd, elongated spermatid. Bars represent the means ± SD of two independent experiments (n = 10 per season). Means within the columns with different marks indicate a significant difference; ** represents p < 0.01.

Figure 2

Immunohistochemistry results of luteinizing hormone receptor (LHR) and follicle stimulating hormone receptor (FSHR) in the testes of plateau zokor (Eospalax baileyi) during the breeding and non-breeding seasons. (A,D): the immune localization of LHR in the testes of plateau zokor, (B,E): the immune localization of FSHR in the testes of plateau zokor, and (C,F): the control using phosphate buffered saline (PBS) instead of the first antibody. Scale bars, 100 µm. SC, Sertoli cell; LC, Leydig cell; Spg, spermatogonia; pSpc, primary spermatocyte; sSpc, secondary spermatocyte; eSpd, elongated spermatid.

Figure 3

Average optical densities of immunopositive signals of luteinizing hormone receptor (LHR) and follicle stimulating hormone receptor (FSHR) during the breeding and non-breeding seasons. (A): average optical densities of immunopositive signals of LHR; (B): average optical densities of immunopositive signals of FSHR. Bars represent means ± standard deviations of two independent experimental treatments (n = 10 per season). Means within columns with different marks indicate a significant difference (** represents p < 0.01).

Figure 4

RT-PCR analysis of the mRNA of plateau zokor (Eospalax baileyi) during the breeding and non-breeding seasons; (A): the mRNA relative expression levels of LHβ and FSHβ in the pituitary gland of plateau zokor (B): the mRNA relative expression levels of LHR and FSHR in the testes of plateau zokor. Bars represent the means ± standard deviation of two independent experimental treatments (n = 10 per season). Means within the columns with different marks indicate a significant difference; * represents p < 0.05, ** represents p < 0.01.